Recently, flat displays have been actively developed. Among them, liquid crystal displays have attracted attention because of their advantages of being light and thin and having low energy requirements. In particular, in active-matrix liquid crystal displays in which a switching element is incorporated into each pixel, a structure in which a lateral electric field (including a fringe electric field) such as an in-plane switching (IPS) mode and a fringe field switching (FFS) mode is used is attracting attention.
Such a liquid crystal display of the lateral electric field mode includes an array substrate which includes a pixel electrode and a common electrode and on a surface of which a first alignment film is formed, a counter substrate in which a second alignment film facing the first alignment film is formed, and a liquid crystal layer enclosed in a cell gap formed between the first alignment film and the second alignment film, wherein a liquid crystal molecule of the liquid crystal layer is switched in a lateral electric field substantially parallel to the main surface of the array substrate.
The alignment treatment by, for example, a rubbing method or a photo-alignment method is performed on each alignment film. If the alignment treatment by the rubbing method is performed on the alignment film, an area in which alignment capability is not fully provided on the alignment film may be produced because of projections and depressions on the alignment film surface. Since a liquid crystal molecule switched by an electric field is hard to return to an initial alignment direction near such an area, so-called burn-in easily occurs. Further, a difference in transmittance is easily visually recognized as display unevenness in a portion in which a difference occurs in the alignment capability because of the projections and depressions in a rubbing treatment.
Further, if the alignment treatment by the photo-alignment method is performed on the alignment film, a color filter may be faded by ultraviolet irradiation of the treatment processing, impurities may be produced by a decomposed member formed of an organic material on a substrate, and the produced impurities may be eluted to the liquid crystal layer.